Due to high absorption capacity and lower costs, natural cellulose fibers are preferred components of many disposable absorbent products, such as diapers, catamenials, and adult incontinence products. The cellulose fibers are provided to manufacturers of disposable absorbent products in the form of fibrous comminution pulp sheets or rolls which are manufactured by conventional wet-laid techniques. Generally, disposable absorbent products are manufactured in a continuous manufacturing process. The disposable product manufacturer typically disintegrates or comminutes the pulp sheets with a hammer mill or similar mechanical apparatus to separate the cellulose fibers into a fluff commonly known as airfelt. Chemically softened pulp is most commonly used in place of untreated pulp, because it is easier to disintegrate on a hammer mill or similar disintegration equipment. Moreover, the use of softened pulp is required on some low powered equipment, such as pin cylinders. The comminution pulp is formed into nonwoven structures known as airfelt pads or airfelts using conventional airlaid techniques, and the airfelt pads are combined with other components to produce the final absorbent product such as a disposable diaper or feminine napkin. The airfelt pads must possess certain characteristics such as a high absorption capacity, strength and integrity, an adequate wicking rate, and other fluid transport properties in order to be suitable for use in disposable absorbent products.
Since the fiber sheets are disintegrated on-line in the diaper manufacturing process, the rate of production of the diapers or other disposable absorbent products is limited by the speed at which the fiber sheets can be disintegrated. Increasing the speed of disintegration requires significantly greater expenditure of energy or capital for larger disintegrated motors and related equipment.
Prior to the present invention, it was known that the amount of energy required to disintegrate pulp sheets could be reduced by adding surfactants to the cellulose fiber pulp. However, the surfactants typically used for this purpose create a hydrophobic, non-wetting surface on the pulp which results in the loss of many of the desired fluid transport properties in airfelts formed from surfactant treated fibers. Further, the surfactants act as a lubricant on the fibers and reduce the fiber to fiber friction required to form an airfelt with strength and integrity.
Therefore, there continues to be a need for natural cellulose fiber pulp for forming pulp sheets which do not require high amounts of disintegration energy and provide well-dispersed airfelt pads which retain the highly desirable characteristics of exceptional strength, absorbency, wicking rate, and other significant fluid transport properties found in untreated cellulose fibers.